Well surveying device



Dec.- 16, 1941.

R. e. P IETY WELL SURVEYING DEVICE s Sheets-Sheet 1 Filed May 31. 1939INVENTOR R. G. PIETY FIG.

l' NEY WELL SURVEYING DEVICE Filed May 31, 1939 3 Sheets-Sheet 2INVENTOR F IG. 2 R. c. PIETY Dec. 16, 1941. R. G. PIETY' 2,266,071-

WELL SURVEYING DEVICE I Filed May 31, 1939 5 Sheets-Sheet 3 lll : I 8 El I INVENT OR R.G. PIETY Patented Dec. 16, .1941

WELL SURVEYING nrzvror: Raymond G. Piety, Bartlesvllle, Okla" assignorto Delaware Phillips Petroleum Company, a corporation of v ApplicationMay 31, 1939, Serial No. 276,7 11

' Claims. (urns-182) This invention relates to improvements in apparatusand method for determining the nature of geological structure byelectrical'means.

In drilling for oil it is desirable to obtain information which willidentify the geological strata being penetrated by the drill hole. It iscustomary when using a rotary drill to take samples of cuttings duringthe drilling operation.

Such samples are easily obtained, butoften donot provide enoughinformation concerning the nature of the structure. been to take coresor cylindrical samples, cut from the rock during the drillingoperations.

This method gives good results but is time con-- suming and expensive.

Certain physical properties of. subsurface strata are detectable byelectrical means and Figure 3- is an enlarged view partly in section andpartly in elevation of the electrode shown in Figures-1 and 2. 1

Figures 4-7 inclusive are views of various modifications of the movableelectrode which may be used.

Referring to Figure 1, the numeral I reiers to a bore hole normallyfilled with water or drilling Another method has drill hole and porousformations which it penetrates, due either to difierences inelectrolytic concentration between the drilling fluid and the formationfluids or to passage of fluid into or out of the rock pores(electrofiltration), also furnishes useful information. I

Methods of determining conductivity and admittance which havebeen-proposed make use of localized electrodes and measure effects atthese electrodes. These methods are limited to a small,

Other objects and advantages will be apparent from the specification andfrom the accompanying drawings. Y

Figure 1 is a vertical sectional view through a I bore hole showing oneform of this invention in operative position.

Figure 2 is a vertical sectional view through a borehole illustrating amodification of this invention.

fluid 2 and piercing various earth strata 3, 4, 5, and 6. A longelectrode 1 which may consist of a bare wireis suspended in the borehole by means of an insulated conductor 8. Conductor 8 is connected toone output terminal of a source of electrical current 9, which has itsopposite output terminal connected to a grounded electrode I0. Groundedelectrode I0 may be placed on the surface of the earth or in the borehole.

A movable electrode I2 consisting of a conducting surface, which may beof the non-polarizing type, is suspended in the bore hole parallel to orconcentric with electrode I and insulated therefrom by an insulatingtube II. Insulating tube II has a sufiiciently small inside diameter tomake the current paths around theends and into that portion of electrode1 within the tube poorly conducting or to introduce a known correction.Electrode I2 is suspended by an insulated conductor I3 which isconnected to the electrical current source 9. A power reel I6 isprovided to move electrode I2 along electrode 1. A recording meter I4 isconnected between current source 9 and electrode I2 to measure thecurrent flowing through conductor I3.

In operation a potential is applied between electrodes I and I2 in thebore hole and grounded electrode III by the currentsource 9, causingcurrent to flow through the intervening earth strata. Either direct oralternating current may be supplied to the electrodes. With movableelectrode I2 in an inoperative position at the surface of the earth,current will enterelectrode I along its entire length, more enteringwhere I the current density is greatest in the formation,

cepted by movable electrode. I2 and flows through conductor I3 andrecording meter I4 to the cur rent source 9. By recording the currentintercepted by movable electrode I2, the extent and relativeconductivity or resistivity of each stratum may be determined.

In- Figure 2, the device is modified to measure the change in phasebetween the current in the main circuit and current entering movableelectrode l2 when alternating current is supplied by the current source9. A meter ll of the dynamometer type or an alternating currentpotentiometer is connected with conductors 8 and I3 and one pole of thealternating current generator. The dynamometer type meter has the fieldcoil and moving coil terminals brought out separately. The deflection ofthe meter will then be proportional to the product of the currents ineach coil multiplied by the cosine of phase angle between the twocurrents, so that if the currents are known the phase angle may be determined. A recording meter 18 is connected between alternating currentsource 9 and conductor 8 to measure the total current flowing fromelectrode to or from the current source.

Figures 3-7 inclusive illustrate various forms of the movable electrodewhich may be used. In Figure 3 a conductor 12 is mounted on the surfaceof an insulating tube H. Figure 4 shows conductor l2 wound in a spiralmanner around the insulating tube, wherea in Figure 5, conductor l2consists'of a long cy inder concentric with and,

mounted on insulating tube I I. Figures 6 and '7 illustrate two forms ofnon-polarizing electrodes which may be used. In Figure 6, conductor i2is immersed in a solution of its salt 20 which is contained in a porousvessel 2| attached to the outside surface'of insulating tube II.' InFigure 7, the electrode illustrated in Figure is surrounded by a porouscylinder 2| containing a saturated salt solution 20. A cover 22 isprovided to prevent mixing with fluid of the bore hole when theelectrode is in operative position.

This system will obtain data which is useful also for approximating theextent to which the strata extend beyond the bore hole, and for locatingnon-conformities or deposits near the bore hole. For example, if one ofthe strata, say 4, is a poor conductor, it will tend to reduce theamount of current reaching the formation below it, but if 4 extendslaterally only a short distance from the bore hole, then by movingelectrode l0 away from the bore hole the currents can flow around 4 andenter the lower layers more readily. Electrode It! may be moved radiallyor circumferentially relative to the bore hole to determine extent ordirection of various strata.

The use of different frequencies offers some control over the currentdistribution; at high frequencies, the current will tend to 'flow nearthe surface. In order to force high frequency current down, theinsulated conductor 8 may be lengthened to extend some distance into thebore hole. Moving electrode III to various positions may 'in the claims.

I claim:

1. A method of electrically logging a bore hole comprising suspending anelongated electrode in the bore hole to be logged, grounding a secondelectrode, setting up an electrical potential be-- those of the firstclaimedcurrent.

2. A method of electrically logginga bore hole comprising suspending anelongated electrode in trode and means for measuring the current in thethe bore hole to be logged, grounding a secondelectrode, establishing anelectrical potential between the two electrodes, interposing a thirdelectrode to intercept current at a point on the elongated electrode,and measuring the current in the third electrode.

comprising a source of electrical potential, an elongated electrodeconnected to one side of the source' and extending into the borehole, agrounded electrode connected to the other side of the source, a thirdelectrode arranged to move 3, Apparatus for elegetrically logging a borehole along the length of the elongated electrode, the

of the current in the third electrode with those of the current in. theelongated electrode.

5. Apparatus for electrically logging a bore hole having fluid thereincomprising a sourceof electrical potential, an elongated electrodeconnected to one side of the source and extending into the bore hole, agrounded electrode connected to the other side vof the source, a thirdelectrode arranged to move along the length of the elongated electrode,the third electrode having means associated therewith substantially toisolate a section of the elongated electrode from the fluid, meansformeasuring the current in the elongated electhird electrode.

RAYMOND G. PIETi I.

